virology lec. 1 Intro to Viruses

Characteristics of viruses

Smaller than bacteria

Obligate parasites, dependent on host cell to reproduce

Genome consists of one type of nucleic acid,DNA, or RNA

Receptor-binding protein

Recent viral epidemics

Covid 19

Zika virus

Ebola

Early virus studies

OG definition: agents that can pass thru filters that trap most known bacteria

Chamberland porcelain ultra filters

Use of electron microscope to visualize viruses

What was the first virus discovered and who did it?

Tobacco mosaic virus (TMV) by Ivanovsky in 1982. Late 1800s

Describe chamberland porcelain ultrafilters

were used to retain or remove bacteria from drinking water (1884). Pasteur and others discovered that unfilterable germs or bacteria could be retained by the filters, visualized by light microscopy, and grown on solid bacteriological media containing agar and as cultures in broths. Made by Charles Chamberland

The Hershey-chase blender experiment

To prove mainly DNA, not protein, is inherited from parental phage

Learning from viruses

Tracking cold sores and human migration

• herpes simplex virus 1: HSV-1

• DNA of different HSV-1 strains helps researchers study migration patterns

• Cladistics

Clad

Figure 1.9: A clade is a section of a phylogenetic tree that extends to current organisms or, in this example, HSV-1. A clade must include all descendants from a common ancestor. In the diagram, the purple and red boxes are clades. The blue box is not a clade because it does not include all descendants from a common ancestor.

Define virome

The complete collection of viruses that live inside a specific organism or environment

Theories of viral origin

Panspermia hypothesis: viruses fell from outer space

• last universal common ancestor (LUCA)

• 5 classes of viral genes

Herpesvirus “protection”

• Latency: dormant state

• Vast majority of viruses that infect us are not bad - evidence that latent viruses form immunity against bacterial pathogens

Viruses on human skin

• Microbiome: total of all microbiota that live on or inside the human body.

• Human microbiome project

• Metagenomics

Aquatic viromes

• influence ecology and diversity, evolution, and health of all aquatic organisms

Application of viruses in health or medicine

Bacteriophage therapy, gene therapy, vaccine development, cancer-causing viruses and virotherapy

Bacteriophage therapy

To fight bacterial superbugs and treatment of bacterial biofilms

Gene therapy

Delivery of functional copies of dysfunctional genes via retroviruses and adenoviruses.

Vaccine development, vaccination

Vaccine development

Edward Jenner’s work with cowpox vaccine and Robert Koch (Koch’s postulates)

cancer-causing viruses and virotherapy

Viral infections linked to approx 12% of all cancers (HPV and cervical cancer)

• Virotherapy: Oncolytic viruses used to kill cancer cells

Explain how viruses are transmitted and cause disease.

Virus → reservoir (source) of virus → transmission to susceptible host (direct or indirect) → portal of entry into susceptible host → portal of exit out of susceptible host

Viruses in history: great epidemics

Measles during civil war

Influenza 1918 pandemic

AID 1980s retrovirus HIV

Covid-19 pandemic 2019 SARS-CoV2

Explain AIDS epidemic

Acquired Immunodeficiency Syndrome (AIDS): 1980s -

Retrovirus human immunodeficiency virus (HIV)

- No vaccine available to prevent HIV

Explain Zika virus outbreak (2016)

• spread by mosquitos and started in Brazil

• Could also spread via sexual transmission and vertically from pregnant women to fetuses

• Affected nervous system with mild symptoms

• Public health agencies issued travel advisories

Influenza 1918 pandemic

Spanish flu

• Said to have started in Kansas

• Targeted healthy adults of 20-40 yrs old

• Extreme lethality and cytokine storms.triggered an over reactive immune response

• War time caused bad living conditions and censorship did not let people know about the virus or how to protect themselves

• Devastating amount of dead people all around the world since war caused people to with the virus to spread everywhere

• Genetic ancestor. Caused by an H1N1 influenza A virus of avian origin, this strain served as the genetic root for future major flu pandemics, including the 1957, 1968, and 2009 outbreaks

Influenza A (H1N1) 2009

First influenza pandemic of 21st century

- Outbreak resulted in various public health initiatives

Middle East Respiratory Syndrome-Coronavirus

(MERS-CoV): 2012–present

- Exact origin unknown

- Dromedary camels studied as a possible animal reservoir

Hantavirus: 1993 (U.S. Four Corners Region)

and 2012 (Yosemite Park)

• Resulting new or emerging infectious disease named hantavirus pulmonary syndrome (HPS)

• Isolated from the deer mouse

• Not contagious human-to-human

Measles

• Once eliminated in 2000 in the U.S., now on the rise

• Results from unvaccinated U.S. residents contracting

disease traveling to/from affected regions

• Contributing factor: Andrew Wakefield

• Published fraudulent report linking MMR vaccine to

autism

• Recent outbreaks underscore importance of viral

immunity and control through vaccination

Ebola Virus Disease in West Africa:

2014–2016

• Bats thought to be an animal reservoir

- Spread rapidly through healthcare and travel

- 28,639 cases and 11,316 deaths as of February 3, 2016

- 2026 outbreak in DRC

• 6250 cases, 3039 deaths as of September 1, 2026